This article was downloaded by: [George Mason University] On: 17 December 2014, At: 20:32 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20

Treatment of the terephthalic acid-containing wastewater using a biological-aerated filter a

a

a

a

Wen-yi Zhang , Cai-qin Zhang , Liang Liu , Rong-yan Shen & Xiao-jing Han

a

a

School of Environmental and Safety Engineering, Changzhou University, No. 1, Gehu Road, Changzhou, 213164, People's Republic of China Accepted author version posted online: 28 May 2013.Published online: 14 Jun 2013.

Click for updates To cite this article: Wen-yi Zhang, Cai-qin Zhang, Liang Liu, Rong-yan Shen & Xiao-jing Han (2014) Treatment of the terephthalic acid-containing wastewater using a biological-aerated filter, Environmental Technology, 35:1, 70-74, DOI: 10.1080/09593330.2013.808269 To link to this article: http://dx.doi.org/10.1080/09593330.2013.808269

PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions

Environmental Technology, 2014 Vol. 35, No. 1, 70–74, http://dx.doi.org/10.1080/09593330.2013.808269

Treatment of the terephthalic acid-containing wastewater using a biological-aerated filter Wen-yi Zhang∗ , Cai-qin Zhang, Liang Liu∗ , Rong-yan Shen and Xiao-jing Han School of Environmental and Safety Engineering, Changzhou University, No. 1, Gehu Road, Changzhou, 213164, People’s Republic of China

Downloaded by [George Mason University] at 20:32 17 December 2014

(Received 22 October 2012; final version received 18 May 2013 ) In this paper, the biological-aerated filter (BAF) was employed to treat the wastewater containing terephthalic acid (TA). Factors that affected the efficiency of TA and CODCr removal were evaluated experimetally, including pH, hydraulic loading, hydraulic retention time (HRT) and TA volume loading. At pH 7–8, hydraulic loading rate 0.067–0.48 m3 /(m2 h), HRT more than 3.5 h and TA loading 0.04—0.15 g/(m3 d), the TA and CODCr removal efficiency was more than 93% and 87%, respectively. The mathematical model of matrix (TA) was obtained by Monod’s relation and the experimental parameters of the model were 1.972 g/(m2 d) and 9.782 mg/L. Keywords: biological-aerated filter; terephthalic acid wastewater; hydraulic loading; TA volume loading

1. Introduction Terephthalic acid (TA) is a petrochemical product, formed via oxidation of paraxylene and by hydrolsis in terephthalonitrile prepared by p-xylene ammoxidation. TA is widely used for the synthesis of chemical fibre, plastic, dyestuff, etc. TA contamination is a serious environmental concern due to its toxicity. In the recent years, the production and consumption of TA increased highly in China. A great quantity of TA wastewater was also produced. Hence, it was important to treat effectively TA wastewater. Acidulation is the commonly used method to treat TAcontaining wastewater. Most of TA in wastewater could be removed by acid recovery, and the removal efficiency of CODCr was very high. But the TA particles by acidification were fine, and the sizes of particles were only about 5 μm.Therefore, it was difficult for deposition and separation, and the poor dewatering ability existed. Furthermore, the aciding-out processes consumed a large amount of acids. Considering the treatment cost, acidification was used only for the pretreatment process of high concentration TA wastewater.[1–4] When the concentration of TA wastewater was about 10–50 mg/L, biological treatment is mainly used at present. Some anaerobic treatment processes, such as up-flow anaerobic sludge bed (UASB),[5,6] biological filter bed,[7] hybrid anaerobic reactor,[8,9] were mostly applied in engineering. In the treatment of TA wastewater by UASB and the anaerobic filter bed, the influent TA concentration was from 40 to 1800 mg/L and the removal rate was usually from 40% to 50%. The decomposition of TA was difficult and the

∗ Corresponding

operation flexibility of the system was low under anaerobic conditions. And the start-up period was long with the weak anti-shock loading capability. The anaerobic treatment was difficult to run stably from the point of the above-mentioned views.[10] Aerobic activated sludge process was used to treat TA wastewater by AMOCO,[11,12] USA and Shanghai No.2 Terylene Plant.[4] Though the process had a good treating effect, it was unavoidable that some disadvantages existed in operation. These disadvantages included sludge bulking, the low capability of anti-shock loading, the big workload in treatment, disposal of excess sludge, etc.[1] Biological-aerated filter (BAF) [13] mainly used its internal filling filter materials and attached biomembranes as treatment media. BAF had many effects, including microbe metabolism, physical filter, physical adsorption and multiple predations in the reactor. So the pollutants and bacteria were removed at a reactor. BAF was characterized by high bioactivity, low energy consumption, little excess sludge, high organic loading, running stability and simple management.[14–16] This research was about exploring the feasibility of BAF to TA wastewater. 2. Materials and methods 2.1. Instrument and equipment The PVC pipe was used in the column of the BAF reactor. The pipe’s diameter was 10.5 cm and the height was 130 cm. The supporting layer was 6 cm in the bottom column. The column was filled with 6.48 L coal-ash ceramsite filter medium, and the height of the packing layer was 90 cm.

author. Email: [email protected], [email protected]

© 2013 Taylor & Francis

Downloaded by [George Mason University] at 20:32 17 December 2014

Environmental Technology

71

Bottom feed, long handle filter nob for spurt water device and the upper water drainage were adopted in the reactor. The sintered sand core aerators were settled (Type YL-888 pump). Air flow rate was 7.9 L/h. A type BTOO-50M constant flow pump was used for water supply. All of the experiments were done at a controlled temperature of 25 ± 3◦ C. Parameters of the coal-ash ceramsite filter media are given in Table 1.

to wash the BAF with air for 5 min and start the pump. Then it was followed by backwash with air–water for 5 min. Finally, washing BAF was done with water for 5–8 min. The back washing effluent was treated in the reactor. Detached biofilm, sludge and other substrates were back to the regulating settling pond with the effluent of back washing and discharged. The precipitated sludge exited through the sludge tank.

2.2. Water quality TA wastewater in the test was artificial, which contained a specified volume of TA, beer and little mount of activated sludge. Beer raised CODCr value and activated sludge enhanced suspended solid (SS). With the proper pH adjustment, the artificial TA wastewater appeared alkalescent. The quality of the simulated wastewater is given in Table 2.

2.4. Cultivation of biofilms in BAF The continuous flow method was adopted to cultivate the biofilms in BAF. Initially, the amount of septic tank effluent was added to the filter and aerated in the filter. After three days of continuous operation, the simulated wastewater containing low concentrations of TA was infused into the filter, and then the mixtures in the filter were adjusted to alkalescence. The CODCr concentrations in influent and effluent were determined during the biofilm culturing in order to know indirectly the growth of microorganisms. About 20 days later, a thin layer of biomembrane developed on the outer surfaces of the filter media. Protozoans such as an amoeba and vorticella could be seen in the biomembrane under a microscope. These protozoans indicated the maturation of the biofilm growth. During this period, the removal efficiencies of CODCr and TA all reached 75%, which meant that the microorganism by acclimation basically adapted to the TA wastewater, and the biofilm was successfully cultured.

2.3. Process flow The diagram of flow process of the test is shown in Figure 1. First, raw water entered a regulating settling pond to adjust pH, then entered into the BAF bottom, finally infused into the filter media layer by the long handle filter nob. Meanwhile, the air pump offered oxygen for the filter media layer, and the outflow was discharged after a storing reservoir. Backwashing was conducted in the reservoir by the combination of air and water at intervals. The method was Table 1.

The parameters of the coal-ash ceramsite filter media.

Parameter names

Parameter values

Diameter/(mm) Bulk density/(g/cm3 ) Specific surface area/(m2 /m3 ) Porosity/(%) Wear rate/(%) Hydrochloric acid dissolubility/(%)

Table 2.

3–5 0.89 372.5 35% 5.30% 0.50%

2.5. Analytical methods of water quality Water and Exhausted Eater Monitoring Analysis Method (4th edition) [17] was used for water monitoring analysis. Chemical oxygen demand (CODCr ) was determined by the potassium dichromate method. The concentrations of TA were analysed by spectrophotometry (752UVspectrophotometer). The pH was determined by the potentiometric method.

The quality of simulated wastewater.

Project

pH

SS/(mg/L)

COD/(mg/L)

TA/(mg/L)

Range Average

7.0–11.0 9.0

100–200 150

160–720 440

10.0–14.0 12

The backwash drainage

3. Results and analysis In this paper, the BAF was adopted to treat the wastewater containing TA. The influence of many factors on the performances of TA and COD removal was studied, such as pH, hydraulic loading, hydraulic retention time (HRT), TA loading etc. The results are described below.

Air pump TA wastewater

Sludge discharge

Figure 1.

Regulating settling pond

Sludge tank

Constant flow pump

The drainage

Biological Aerated Filter

Backwash pond

Backwash pump

Process scheme of experiment investigation.

3.1. pH, hydraulic loading and TA removal rate As the influent of TA concentration ranged from 10 to 12 mg/L, under different hydraulic loading, the relationship between pH and the removal rates of TA is represented in Figure 2. It showed that the highest removal rate of TA was at pH 7.0–8.0 under the same hydraulic loading condition. This illustrated that the pH range of 7.0–8.0 benefited

72

Downloaded by [George Mason University] at 20:32 17 December 2014

Figure 2. rate.

W.-y. Zhang et al.

Influence of pH and hydraulic loading on TA removal Figure 3.

Relationship of HRT and TA removal rate.

microbial growth. Meanwhile, when pH was from 7 to 10, the removal rates of TA increased at the beginning, then dropped later with increase in hydraulic loading. In this case the removal rate of TA had no linear relationship with hydraulic loading. Because hydraulic loading and organic loading were lower, microorganisms were malnourished. Furthermore, nutritional deficiencies could influence the removal of organic matters dissolved in wastewater. Under high hydraulic loading, the reaction of TA wastewater and carrier biofilm could occur successfully in the reactor. High hydraulic loading caused an increasing scour of the membrane surface which was beneficial for the renewal of biofilm. Therefore, the reactor had an advantage of high removal of pollutants at high hydraulic loading. Hydraulic loading was too high and contact time was too short. So, the pollutants in the BAF were never sufficiently degraded and the removal rates declined. Thus, under pH 7.0–8.0 and hydraulic loading between 0.067 and 0.48 m3 /(m2 h), the removal rate of analog TA wastewater could sustain 80% of the BAF process. At pH 7.1, when hydraulic loading was 0.215 m3 /(m2 h), TA removal rate reached 93.02% and TA concentration in effluent was 0.72 mg/L.

Figure 4. rate.

Relationship of TA volume loading and TA removal

3.2. HRT and TA removal rate The effect of HRT on TA removal was studied at pH 7.0–8.0 and TA concentration 10–12 mg/L. The results are shown in Figure 3. The graph showed that the TA removal rate increased with increase in HRT. When HRT was over 2 h, the removal rate of TA was above 80%. When HRT was over 3.5 h, TA removal rate was almost invariable, remaining 92%. And TA concentration in effluent was 0.71 mg/L. It meant that at short HRT, the wastewater did not fully react with the microorganism attached to the filter material. As a result, only part of TA could be digested and absorbed by microorganism. With increase in HRT, the microorganism could fully be in contact with TA wastewater, and assimilated TA easily and improved TA removal. But when HRT reached a certain value, the reaction stopped completely. At the moment, the degrading ability of the biofilm reached the peak and TA removal rate could not increase again.

3.4.

3.3. TA volume loading and TA removal rate At pH 7.0–8.0, HRT from 2 to 7 h and the influent TA concentration 10–12 and 12–14 mg/L, the relationship between the influent TA loading and TA removal rate was studied (as shown in the Figure 4). When TA volume loading varied from 0.02 to 0.15 kg/(m3 d), TA removal rate increased first and decreased afterwards (influent TA concentration 10–12 mg/L). It reached its maximum when TA volume loading was about 0.15 kg/(m3 d) and the TA removal rate was over 80%. At this time, the TA concentration in the effluent was 0.82 mg/L. When the influent TA concentration was 12–14 mg/L, the TA removal rate was 87.35– 73.62%, respectively, and TA concentration in effluent was 3.43 mg/L. Experimental results indicated that TA removal rate reduced with the increase in TA volume loading. As TA volume loading remained unchanged, TA removal rate also reduced with the increase in TA influent concentration.

CODCr degradation and TA removal rate Under the conditions of various hydraulic loading, the curve between CODCr and TA removal rates was obtained (Figure 5). As shown in Figure 5, the degradation rates of CODCr and TA basically presented the descent trend at the same time. The biological hydrolysis and synchronous biological degradation happened in the TA wastewater. The removal rate of TA was larger than the degradation rate of CODcr, because TA was a kind of organic

Environmental Technology

73

Figure 6.

The relation between 1/U and 1/Se .

Figure 7.

The relation between U /(Umax − U ) and Se .

Downloaded by [George Mason University] at 20:32 17 December 2014

Figure 5. Relationship of CODCr degradation efficiencies and TA removal rate.

matter, it was also one of the components of CODcr in wastewater. And it was removed firstly. From the study of Martin Alexander, we know that the carboxyl (−COOH) and phenolic hydroxyl (−OH) can heighten the degradation rate of microorganisms.[18] The degradation pathway of TA through aerobic activated sludge was given by He and Zhang [19] and the others. The degradation pathway is as follows. TA became 3-hydroxy TA, then became m-hydroxybenzoic acid (IV) and protocatechuic aci (3,4dihydroxybenzoic acid). In the end, protocatechuic acid could be completely degraded into CO2 and water. 3.5. Degradation dynamics of TA Biodegradation kinetics of TA could be represented by the Monod equation (Equation (1)), and the degradation process followed the reaction dynamics [20] Umax · Se U = , (1) Ks + S e Q(S0 − Se ) U = , (2) N ·Q 1 Ks 1 1 = · + , (3) U Umax Se Umax Umax · Se . (4) U = Ks + S e In the above equation, U is the removal rate of the filler– matrix per unit area (g/m2 d), and U was obtained from Equation (2), where Q is the influent flow (m3 /d), S0 is the concentration of influent substrate (mg/L), Se is the concentration of the influent substrate (mg/L), N is the filler volume (m3 ), a the specific surface area of the filler (m2 /m3 ), Umax is the maximal removal speed of the filler–matrix per unit area (g/m2 d), Ks is the saturation constant, and its value was the substrate concentration at U = Umax /2 (mg/L). And Equation (3) is the reciprocal of Equation (4). The drawing was plotted with 1/U and 1/Se , and their correlations are shown in Figure 6. According to Figure 6, Umax (1.972 g/(m2 d)) and Ks(9.782 mg/L) were obtained. But the non-biodegradable

substance existed. Thus, considering Equation (4), the following equations could be deduced: U =

Umax · (Se − Sn ) , Ks + (Se − Sn )

(5)

U · Ks + U (Se − Sn ) = Umax · (Se − Sn ),

(6)

U · Ks + Sn (Umax − U ) = Se · (Umax − U ),

(7)

Se = Ks ·

U + Sn . Umax − U

(8)

If Equation (8) and the data in Table 2 were applied, a plot using Umax and Ks should yield a straight line, and the slope was Ks . Figure 7 showed the aforementioned representation for experiments carried out under operating conditions. Y intercept of line was the concentration of nonbiodegradable substance (Sn = 0.3254 mg/L). The value of Ks was theoretically calculated at the 8.5067 mg/L. The error was 13% compared with the value of Ks by Figure 6, taking Ks = 9.782 mg/L. Degradation kinetic models of TA in BAF reactor were built by taking Ks as 9.782 mg/L in Equation (5) U =

1.972 × (Se − 0.3254) . 9.782 + (Se − 0.3254)

(9)

The value of U was calculated by Equation (9) and linear regression was made with the value of U obtained through experiments. Consequently, R was 0.9944. By verifying

74

W.-y. Zhang et al.

correlation coefficient test table R0.01 (n − 2) was 0.959, so R was more than R0.01 (n − 2). This adequately proved that the correlation between estimated values of a mathematical model and observed values was highly significant. Therefore, the creation and application of this model had certain theoretical guidance meaning and practical reference value.

Downloaded by [George Mason University] at 20:32 17 December 2014

4.

Conclusions (1) When the influent TA concentration was from 10 to 12 mg/L, the temperature was from 21 to 28◦ C, pH was 7.0–8.0, hydraulic loading was 0.067– 0.48 m3 /(m2 h), and HRT was more than 2 h, TA removal rate remained over 80% in the treatment of simulated TA wastewater by BAF. When hydraulic loading was 0.215 m3 /(m2 h), and pH was at 7.1, the TA removal rate reached 93.02% and the effluent TA concentration was 0.72 mg/L. (1) The removal rate of TA declined with the increase in TA volume loading. When TA concentration ranged from 10 to 12 mg/L and TA volume loading ranged from 0.02 to 0.15 kg/(m3 d), the removal rate of TA was above 80%. (2) The degradation of CODCr and the TA removal in wastewater basically had a same descent trend. It showed that biological hydrolysis and synchronously biological degradation happened in the TA wastewater. And the removal rate of TA was larger than the degradation rate of CODCr . It further indicated that TA decomposing should first occur in the BAF reactor. According to the Monod equation, degradation kinetic model of TA in BAF reactor was given and the kinetics parameters were as follows. Umax was 1.972 g/(m2 d), and Ks was 9.782 mg/L. At the same time, the experimental data had a significant correlation with the kinetics parameters. Therefore, the model had a extremely high reference value.

Acknowledgements The authors wish to acknowledge Water Treatment Model Simulation Open Laboratory (Changzhou University, China) for facilitating in carrying out the water quality analysis. This research was supported by the Natural Science fund of the Jiangsu Province (Project Number: BK200930405, BE201077311) and the Natural Science Fund Social Development Project of Changzhou City (Project Number: CS20100015, WS201003).

References [1] Guan B, Xu G, Zhao D, Wang K. Treatment technology of wastewater containing terephthalic acid. Technol Water Treatment. 2002;28:129–133.

[2] Zhang X, Cheng S, Lu J. Control of toxicities from terephthalic aid and its wastewater. Techniques Equipment Environmental Pollution Control. 2003;4(12):6–11. [3] Wen Y, Tong S, Zheng K, Wang L, Lv J, Lin J. Removal of terephthalic acid in alkalized wastewater by ferric chloride. J Hazardous Mater. 2006;138:169–172. [4] Li G, Shen L. Pure terephthalic acid wastewater treatment. China Biogas. 1995;13:1–6. [5] Carlos R, José LR, Cristina L. Anaerobic digestion of the liquid fraction of dairy manure separated by screw pressing and centrifugation in a upflow anaerobic sludge blanket reactor at 25◦ C. Biosystems Eng. 2012;112(4):344–351. [6] Shi R, Xu H, Zhang Y. Enhanced treatment of wastewater from the vitamin C biosynthesis industry using a UASB reactor supplemented with zero-valent iron. Environ Technol. 2011;32(16):1859–1865. [7] Wang G, Jin Y, Shen Y. Alkali minimization and dyeing wastewater treatment in production of artificial silk fabrics. Environ Protection. 1998;2:21–23. [8] Tawfik A, El-Kamah H. Treatment of fruit-juice industry wastewater in a two-stage anaerobic hybrid (AH) reactor system followed by a sequencing batch reactor (SBR). Environ Technol. 2012;33(4):429–436. [9] Kleerebezem R, Ivalo M, Pol LWH, Lettinga G. High rate treatment of terephthalate in anaerobic hydrid reactors. Biotechnol Progress. 1999;15:347–357. [10] Li X, Chen J, Lun S. Anaerobic degradation kinetics for organic wastewater containing terephthalic acid(TA). China Environ Sci. 2000;20:27–30. [11] Zheng R. The analysis on treatment technology of terephthalic acid wastewater by U.S. AMOCO[J]. Environ Protection Chem Industry. 1991;11:152–156. [12] Soni RK, Soam S, Dutt K. Studies on biodegradability of copolymers of lactic acid, terephthalic acid and ethylene glycol. Polymer Degradation Stability. 2009;94: 432–437. [13] Lim T, Jin Y, Ni J, Heber AJ. Field evaluation of biofilters in reducing aerial pollutant emissions from a commercial pig finishing building. Biosystems Eng. 2012;112: 192–201. [14] Zheng J. Engineering examples and new techniques of wastewater treatment by aerated biological filter [M]. Beijing: Chemical Industry Press; 2002. p. 78–90. [15] Kent TD, Fitzpatic CSB, Williams SC. Testing of biological aerated filter BAF media. Water Sci Technol. 1996;l34: 363–370. [16] Manikavasagam K, Nishant D, Pradyumna P, Tapas N. Biodegradability enhancement of purified terephthalic acid wastewater by coagulation–flocculation process as pretreatment. J Hazardous Mater. 2008;154:721– 730. [17] Wei F, Qi W, Bi T, Sun Z, Huang Y, Shen Y. Water and exhausted water monitoring analysis method. 4th ed. Beijing: China Environmental Science Press; 2002. [18] Martin AM, Lustigman BK. Effect of chemical structure on microbial degradation of substituted benzenes. J Agric Food Chem. 1996;14:410–413. [19] He X, Zhang Z, Ma S. Study on biodegradability of terephthalic acid. Environ Sci. 1992;13:18–25. [20] Gu X. A mathematic model on biological treatment of wastewater. 2nd ed. Beijing: Tsinghua University Press; 1993. p. 45–76.

Treatment of the terephthalic acid-containing wastewater using a biological-aerated filter.

In this paper, the biological-aerated filter (BAF) was employed to treat the wastewater containing terephthalic acid (TA). Factors that affected the e...
318KB Sizes 3 Downloads 3 Views